Electrical filters are used in the most wide-ranging technical processes for removing dust from gases. In such processes, a packet of separation electrodes is arranged in the gas stream, and spray electrodes, preferably in the form of wires, are inserted between these electrodes, a high DC voltage of the order of magnitude of about 40-150 kV being applied between the electrically parallel connected spray electrodes on the one hand and the separation electrodes on the other. As a result of this, the gas molecules are ionized and then give up their charge to the dust particles contained in the gas stream; these particles are negatively charged and as a result are drawn to the positively charged part of the electrodes. Here, they can be released by vibration or by means of stripping devices and then drop into a dust collection apparatus.
This principle enables widely differing particles to be separated from a wide range of gas streams, which, however, results in strongly varying operating parameters for an electrical filter depending on the application.
To increase the efficiency of existing electrical filter installations, new technologies for generating high voltages (converter systems) and/or optimizing the filter operation (PC-based optimization software) are being developed for example, as a result of which higher separation capacities and/or operation with lower energy consumption are made possible. Verification of the increased efficiency resulting from the use of these new technologies/optimizations is frequently required in advance. However, this verification cannot be theoretically determined in advance due to the complex influencing factors and changing operating parameters of the electrical filters. Test installations having one or more test units, which provide the verification under given operating conditions over an extended test phase (e.g. 1 month), are therefore produced.
When, for example, the new high-voltage generators consist of a converter control cabinet and a special high-voltage rectifier, then these must temporarily replace the existing high-voltage installations for test operation. To provide verification, a clean gas dust measurement and an energy consumption measurement are also required. The complexity and the necessary installation material for the test installation vary depending on the given local installation conditions and the existence of the necessary measuring systems, and must be engineered individually.
Previously, the new converter control cabinets have had to be erected in the vicinity of the control cabinets to be replaced to enable existing power and control cable connections to be reused. However, depending on the local space conditions, this is not possible in all cases, as a result of which new cables have to be laid temporarily. With existing mains voltages of more than 500 V, additional autotransformers, for example, for which a mounting location also has to be found, are often necessary. The expenditure for the changeover (transport/erection/disconnection and termination of the power/control cables) is therefore very high.
In addition, the existing high-voltage rectifiers are usually installed either in transformer pens or on the filter roof. The space conditions in the transformer pens do not usually allow further test equipment to be erected, as a result of which the existing high-voltage devices must first be removed and later refitted (which, depending on the possibility of transportation inside the building, may no longer be possible). When the equipment is erected on the filter roof, the cost of the temporary installation is likewise very high, as a crane and mechanical modifications are required for making the high-voltage connection.
As the electrical filter installation is out of operation during the conversion, the changeover to the test installation and later the reconversion to the existing equipment must be realized within the shortest possible time. The aforementioned conversion effort is however extremely high and requires significantly long down times.
Furthermore, when test installations have been erected in the past, these have sometimes been exposed to difficult ambient conditions (ambient temperature, air pollution etc.). In addition, the units are often damaged when being transported to and in particular within the installations, as a result of which a cost-intensive functional check/repair/cleaning is required before operation can be resumed.